Implement automatic loading of directory buildfiles

Now instead of explicitly writing:

d = foo/ bar/
./: $d
include $d

We can (usually) just write:

./: foo/ bar/

1 files changed, 1 insertions, 1 deletions

diff --git a/build2/file.ixx b/build2/file.ixx
index 44eab91..050a3e9 100644
--- a/build2/file.ixx
+++ b/build2/file.ixx
@@ -4,7 +4,7 @@
 
 namespace build2
 {
-  inline void
+  inline bool
   source_once (const path& bf, scope& root, scope& base)
   {
     return source_once (bf, root, base, base);